title: Ovarian cancer G protein-coupled receptor 1 is involved in acid-induced apoptosis of endplate chondrocytes in intervertebral discs.
abstract: Ovarian cancer G protein-coupled receptor 1 (OGR1) has been shown to be a receptor for protons. We investigated the role of proton-sensing G protein-coupled receptors in the apoptosis of endplate chondrocytes induced by extracellular acid. The expression of proton-sensing G protein-coupled receptors was examined in rat lumbar endplate chondrocytes. Knockdown of OGR1 was achieved by transfecting chondrocytes with specific short hairpin RNA (shRNA) for OGR1. Apoptotic changes were evaluated by DNA fragmentation ELISA, electron microscopy, and flow cytometry. Intracellular calcium ([Ca(2+) ]i) was analyzed with laser scanning confocal microscopy. The mechanism of OGR1 in acid-induced apoptosis of endplate chondrocytes was also investigated. We found that OGR1 was predominantly expressed in rat endplate chondrocytes, and its expression was highly upregulated in response to acidosis. Knocking down OGR1 with shRNAs effectively attenuated acid-induced apoptosis of endplate chondrocytes and increased [Ca(2+) ]i. Blocking OGR1-mediated [Ca(2+) ]i elevation inhibited acid-induced calcium-sensitive proteases such as calpain and calcineurin, and also inhibited the activation of Bid, Bad, and Caspase 3 and cleavage of poly (ADP-ribose) polymerase (PARP). OGR1-mediated [Ca(2+) ]i elevation has a crucial role in apoptosis of endplate chondrocytes by regulating activation of calcium-sensitive proteases and their downstream signaling.
authors.affiliation: Department of Orthopedic Surgery, Zhongshan Hospital, Fudan University, Shanghai, China.
authors.forename: Feng-Lai
authors.initials: FL
authors.lastname: Yuan
authors.forename: Hui-Ren
authors.initials: HR
authors.lastname: Wang
authors.forename: Ming-Dong
authors.initials: MD
authors.lastname: Zhao
authors.forename: Wei
authors.initials: W
authors.lastname: Yuan
authors.forename: Lu
authors.initials: L
authors.lastname: Cao
authors.forename: Ping-Guo
authors.initials: PG
authors.lastname: Duan
authors.forename: Yun-Qi
authors.initials: YQ
authors.lastname: Jiang
authors.forename: Xi-Lei
authors.initials: XL
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Dong
mesh_terms: D000138:Acidosis / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019703:Calcineurin / Q000096:biosynthesis; D002118:Calcium / Q000378:metabolism*; D002154:Calpain / Q000096:biosynthesis; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007403:Intervertebral Disc / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D011522:Protons; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000096:biosynthesis / Q000502:physiology*
chemical_list: C000590690:LOC102553138 protein, rat; D011522:Protons; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; D019703:Calcineurin; D002154:Calpain; D002118:Calcium
keywords: APOPTOSIS; CALCIUM; CALCIUM-SENSITIVE PROTEASES; ENDPLATE CHONDROCYTES; OGR1